Microbes have evolved high affinity iron transport systems which utilize specific Fe3 ion chelating compounds as metal carriers ("siderophores"). Previous experience indicates that upon metal-coordination the siderophores' structures become stabilized in well defined conformations which are amenable to study by heteronuclear NMR spectroscopy. It is proposed to study the siderophores schizokinen, ferribactin, ferrioxamine E and N,N',N" triacetylfusarinine C by combined 1H, 13C and 15N-MR. Decoupling of spin-spin coupled heteronuclei will be used to derive the primary structure of ferribactin while Overhauser effects will provide conformational information. A gated-tailored excitation routine will be implemented in the correlation mode to extract the r-6 dependence of specific interacting dipole pairs. The symmetry of the metallo chromophore will be investigated by NMR spectroscopy of an adequate quadrupolar probe, e.g. 27Al or 71Ga, whose resonance line width ought to sense electric field gradients at the active site.